There seems to be no industry standard gas key sealant. The TM manual I have does not say either.
http://pdf.textfiles.com/manuals/MILITARY/Army%20M16A2%20and%20M4%20manual.pdf
Other than info stating to fire a few to let carbon act as a sealant, this is the only one I’ve ever seen to reference Permatex.
Thanks!
You bet.
SOTAR has a couple of YT videos that talk about it. I think he uses some sort of shellack.
Check out his video here:
https://youtu.be/GCFAtcV1c8k
as with other things in life… I go in dry…
I believe you would be more likely to create a problem than solve one using a sealant. A thin shellac would be better than a thicker gasket sealant though.
Since using nothing works, I’ll stick with that.
ETA: I don’t have my notes with me from Will’s class. I’m in Prescott, AZ this week. I seem to recall him saying machine tolerance should be enough. I can update when I get home. Assuming I remember, before I head to Denver Monday night. Attending his armorers class (which I considered very good instruction) is as close as I come to being an honest mechanic. I generally go with the title “shadetree gun butcher” just to keep myself honest.
I’ve sealed and not sealed and never had a problem either way. If I was to build a BC today, I would not use sealant.
I haven’t done a key install in years. But I lap the surface and was using some rockset on a few. I think someone said rockset was not a good idea, but I never had any leakage issues.
I reached out to BCM, Sionics, Toolcraft, and Aim Surplus. They all report using Permatex Aviation Form A Gasket.
I then contacted Permatex. Permatex Aviation Form A Gasket 80017 and 80019 are the same product. 80017 is 16oz. and 80019 is 4oz. The 3D was an old numbering system that is no longer used.
Contacting manufacturers for accurate information goes against the whole point of the internet. 
Sometimes the manufacturers wont give you the information you want. In this case they did.
Apparently Permatex Aviation is the industry standard.
Double post
I was being a smart aleck.
IE: “The internet is for misinformation and lies, not actual facts” 
LMT uses something from Loctite, I believe it’s gasket sealant 518. I have a little bottle of it for gas keys, but I prefer to use nothing.
Not on the lmt carrier I changed a key on a few weeks ago…that had screws that were not torqued before staking… Guess whoever assembled it also didn’t put sealant on it.
Wow, you wouldn’t expect that from LMT… I recall getting one LMT enhanced carrier without the sealant (might have been my last a few years ago), but they were all torqued to spec and were probably the most difficult gas key screws I’ve ever had to break loose.
518 is what I use. I bought it last time I did some research on it. I doubt using it or not matters, but OCD. One tube will probably last a lifetime for me. I generally avoid effing with gas keys.
yea thats why I buy LMT stuff. This was from circa 2013 or so I guess. Gun ran fine suppressed, but un-suppressed it was erratic. I originally placed blame on running an H2 buffer(shared lower with 9" 300blk upper) and it being a 10.5", then I found the gas key was loose. I had emailed LMT a few times back in 2014 or so when I first realized the key was loose to attempt to warranty it. Never got a response to fix it under warranty and it wasnt a huge deal to me. Life changed and I wasnt able to shoot near as much so a lot of stuff moved the back burner. Recently built another SBR lower so this upper was going back into the rotation so I needed to change the gas key. Staking broke free easily enough(it LOOKED good) and I saw no evidence the screws had actually moved in the staking. Went back on with a BCM gas key and some OCKS screws. Gun functions 100% now.
Long story short, at least in 2012-2013 time frame LMT did NOT use any kind of sealant under the gas key. Standard M16 carrier.
The take-away for me is; we have the formula for doing the job right. If you’re doing a field repair and don’t have the right sealant, I get it. But if I’m at my bench I’m going to stick to the proper standard.
Lap the key, ensure both surfaces are clean, apply the Permatex, the OCKS screws, and 58 in lbs of torque. Then stake the carrier key using a MOACKS.
Note; Lightly dipping a straw into the Permatex container and then carefully placing the straw over the gas port hole of the carrier makes a neat circle around the the gas port hole.
After that I run a pipe cleaner through the gas key to remove any excess that may have gotten into the gas pathway.